Impact of fracture stratigraphy on the paleo-hydrogeology of the Madison Limestone in two basement-involved folds in the Bighorn basin, (Wyoming, USA) Mickael Barbier a, b, ⁎, Rémi Leprêtre a, c , Jean-Paul Callot d , Marta Gasparrini a , Jean-Marc Daniel a , Youri Hamon a , Olivier Lacombe c , Marc Floquet b a IFPEN; 1‐4 avenue de Bois Préau, Rueil-Malmaison, 92852, France b UP, LGSC EA4234, F-13331 Marseille, France c ISTeP, UMR 7193 UPMC and CNRS, F-75005, Paris, France d LFC-R, UPPA, I.P.R.A. Avenue de l'Université BP 1155, Pau 64013 Cedex, France abstract article info Article history: Received 22 November 2011 Received in revised form 18 June 2012 Accepted 27 June 2012 Available online 4 July 2012 Keywords: Fluids Veins Fold Paleohydrogeology Sheep Mountain Rattlesnake Mountain Based on the study of the Madison Limestone at Sheep Mountain and Rattlesnake Mountain, a unique outcrop dataset including (1) facies and diagenetic analyses, (2) vertical persistence and cement stratigraphy of vein sets and (3) fluid inclusions thermometry are used to demonstrate the impact of folding and fracturing on paleo-hydrogeology. Quantification of the vertical persistence of fractures shows that Sheep Mountain and Rattlesnake Mountain differ by the vertical persistence of the pre-folding Laramide vein sets, which are strict- ly bed-confined in Sheep Mountain but cut across bedding at Rattlesnake Mountain, whereas the syn-folding veins are through-going in both. The emplacement chronology and the various sources of the fluids respon- sible for the paragenetic sequence are based on isotope chemistry and fluid inclusions analysis of the matrix and vein cements. At Sheep Mountain and Rattlesnake Mountain, the cements related to the burial are char- acterized by isotopic signatures of marine formation waters that were diluted during the karstification of the Madison Platform at the end of Mississippian. Meteoric fluids, presumably migrating during the Cenomanian from Wind River Range and Teton Range, recharge zones located in the south-west of the Bighorn Basin, were remobilized in the early bed-confined and through-going syn-folding veins of the Sheep Mountain Anticline. The former vein set drained only local fluids whose isotopic signature relates to an increase of temperature of the meteoric fluids during their migration, whereas the latter set allowed quick drainage of basinal fluids. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The characterization of fractured carbonate reservoirs aims at identifying potential fluid flow and hydrocarbon migration pathways, which is an issue considering the high degree of heterogeneity at var- ious scales from the pore to the field. Fractures are the most effective mechanism of reservoir damage at low effective confining pressure, and deeply impact the subsurface oil and gas reservoir properties. Because subsurface data such as cores, well and image logs do not provide enough information to properly characterize the fracture network geometry or connectivity (e.g. Angerer et al., 2003; Lynn, 2004a, 2004b) analogue outcrop studies are essential (Ahmadahdi et al., 2008; Barbier et al., 2012a, 2012b; Beaudoin et al., 2011; Fischer et al., 2009; Gross, 1993; Gross et al., 1995; Hanks et al., 1997; Katz et al., 2006; Lacombe et al., 2011; Travé et al., 2000; Wennberg et al., 2006, 2007). The role of folding, layering, and rock properties on fracture de- velopment has been extensively studied in the past few years in order to understand the factors that control the geometry of frac- ture networks. Following early works (Stearns and Friedman, 1972), several authors have developed a conceptual model relating to folding and fracturing (e.g. Bergbauer and Pollard, 2004; Hennings et al., 2000; Price and Cosgrove, 1990), some of which in- clude the role of the pre-existing fractures and faults in perturbing the stress field at local (Bergbauer and Pollard, 2004; Guiton et al., 2003; Sassi et al., 2012) or large scales (Chester, 2003; Savage and Cooke, 2004). The understanding of the controls exerted on the vein network by the distribution of mechanical properties as well as stratigraphic interface properties has made significant progress (e.g. Barbier et al., 2012a; Laubach et al., 2009). The concept of strat- igraphic control on fracturing has been applied to opening-mode fractures (mode I) and it is now well established that such fractures influence diagenetic history and the hydraulic behavior of strata (Cooke et al., 2006; Fischer et al., 2009; Gross et al., 1995; Lorenz et al., 2002; Shackleton et al., 2005; Wennberg et al., 2006). A clear distinction is now made between the mechanical stratigraphy, which describes sedimentary beds as successive units characterized Tectonophysics 576–577 (2012) 116–132 ⁎ Corresponding author at: TOTAL, CSTJF, BA2010, Avenue Larribau, 64018 Pau, France. Tel.: +33 7 61 71 70 32. E-mail address: mickael.barbier@total.com (M. Barbier). 0040-1951/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.tecto.2012.06.048 Contents lists available at SciVerse ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto